1. Field of the Invention
The present invention relates to magnetic sensors. More specifically, the present invention relates to a magnetic sensor in which a plurality of magnetoresistive elements are aligned in a direction which intersects the passing direction of an object to be magnetically detected at a predetermined angle, for example, at a right angle.
2. Description of the Related Art
Referring to FIG. 7, a magnetic sensor 1 and a magnetic card 6 to be detected by the magnetic sensor 1 will be described.
In FIG. 7, the magnetic card 6 includes a plurality of magnetic patterns 15, which are aligned in the longitudinal direction of the detecting surface of the magnetic sensor 1. The magnetic patterns 15 correspond to data recorded in the magnetic card 6.
The magnetic sensor 1 includes a plurality of magnetoresistive elements 3, which are aligned in the longitudinal direction of the detecting surface of the magnetic sensor 1 so that the magnetic patterns 15 can be read.
When the magnetic card 6 moves in the direction indicated by an arrow a in FIG. 7 so as to approach the magnetic sensor 1 and passes over the detecting surface, each magnetoresistive element 3 of the magnetic sensor 1 magnetically senses each magnetic pattern 15 of the magnetic card 6 individually and outputs a detection output signal corresponding to the magnetic sensing. The detection output signals of the magnetic sensor 1 are applied to a processing circuit (not shown) for signal processing. Accordingly, the data recorded in the magnetic card 6 is processed.
The magnetic patterns 15 on the magnetic card 6 and the magnetoresistive elements 3 of the magnetic sensor 1 are aligned at predetermined intervals so that the data recorded in the magnetic card 6 in the form of the magnetic patterns 15 can be detected by the magnetic sensor 1.
In this configuration, when the interval between the adjacent magnetoresistive elements is large and when the alignment intervals of the magnetic patterns 15 of the magnetic card 6 vary, the correspondence between the magnetic patterns 15 and the magnetoresistive elements 3 of the magnetic sensor 1 is eliminated. As a result, the magnetic sensor 1 cannot accurately detect the magnetic patterns 15 on the magnetic card 6.
The applicant of the present application has proposed a magnetic sensor for reliably detecting each magnetic pattern even when the alignment intervals of the magnetic patterns vary. This magnetic sensor is disclosed in Japanese Unexamined Patent Application Publication No. 5-332703.
This magnetic sensor 1 includes a housing 2, as shown in FIG. 7. A long groove 20 is provided at approximately the center of the detecting surface of the housing 2. The long groove 20 extends in the longitudinal direction of the housing 2. Also, a plurality of the magnetoresistive elements 3 are aligned in the longitudinal direction of the groove 20 such that the magnetoresistive elements 3 contact each other.
At this time, by arranging the magnetoresistive elements 3 so that the gap between magnetic sensitive units 10 of the adjacent magnetoresistive elements 3 is shorter than the width of each of the magnetic patterns 15, the magnetic patterns 15 can be detected even when the alignment intervals of the magnetic patterns 15 of the magnetic card vary.
In order to improve the above-described magnetic sensor, the applicant of the present application has made further investigations and has discovered the following problems regarding the magnetic sensor.
As shown in FIG. 4, the magnetic sensitive unit 10 of each of the magnetoresistive elements 3 used in the magnetic sensor 1 includes a pair of magnetic sensitive portions 14a and 14b. Each of the magnetic sensitive portions 14a and 14b is formed by aligning a plurality of unit magnetic sensitive portions j in the horizontal direction such that the unit magnetic sensitive portions j are connected in series. The magnetic sensitive portions 14a and 14b are disposed on a substrate 19 with a predetermined gap therebetween.
However, as shown in FIG. 4, in each of the magnetoresistive elements 3, the regions between the two horizontal ends of the magnetic sensitive portion 10 and the two horizontal ends of the substrate 19 do not have a magnetic-sensing function and a magnetic-electric converting function. These regions are referred to as magnetically insensitive regions L, which cannot detect the magnetic patterns 15.
Accordingly, when the magnetoresistive elements 3 are aligned in the horizontal direction as in the above-described magnetic sensor, the magnetically insensitive regions L (for example, about 125 μm) of each magnetoresistive element 3 are combined with the magnetically insensitive regions L of the adjacent magnetoresistive elements 3, and thus, a relatively large magnetically insensitive region H is formed (see FIG. 7).
On the other hand, when the alignment intervals between the magnetic patterns 15 on the magnetic card 6 or the positional relationship of the magnetic patterns 15 and the magnetoresistive elements 3 varies, the position of each of the magnetic patterns 15 may be moved from the position indicated by the solid line which corresponds to the magnetic sensitive unit 10, to the position indicated by the broken line, which does not correspond to the magnetic sensitive unit 10, as shown in FIG. 7. As a result, the detection output of the magnetic pattern by the magnetic sensor 1 is decreased and thus the detection sensitivity may be decreased.
Also, in this magnetic sensor, the magnetoresistive elements are aligned along one line in the longitudinal direction of the detecting surface. Therefore, when the magnetic pattern approaches the magnetoresistive elements so as to cover the region between adjacent magnetoresistive elements, this causes crosstalk, that is to say, the detection output for the same magnetic pattern is simultaneously supplied from two magnetoresistive elements to a magnetic card data processing circuit. Consequently, a problem occurs when the processing of the data recorded in the magnetic card is performed in the processing circuit.